1. Field of the Invention
The present invention relates to a piston type compressor having a suction structure with a suction valve, capable of flexural deformation for opening and closing a suction port, for sucking a gas from the suction port into a cylinder bore, by pushing the suction valve to open under a sucking operation of each piston in the cylinder bore.
2. Description of the Related Art
When a gas is sucked from a suction chamber into a cylinder bore in a piston type compressor, the facility or ease of the inflow of the gas greatly affects volumetric efficiency.
A suction port disclosed in Japanese Unexamined Patent Publication (Kokai) No. 57-97974 is circular and a suction port disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2000-54961 is somewhat rounded and substantially triangular. A gas passing through the suction port from a suction chamber towards a cylinder bore exclusively flows in a direction perpendicular to a contour line of the suction port, as viewed from the reciprocating direction of a piston, (the circular port in Japanese Unexamined Patent Publication (Kokai) No. 57-97974 and the rounded triangular port in No. 2000-54961) and enters the cylinder bore. The opening gap of the suction valve relative to the valve plate becomes progressively greater towards the distal end of the suction valve. It is therefore effective to let the gas passing through the suction port flow in the longitudinal direction of the suction valve from its distal end side in order to improve facility of the inflow of the gas. The gas passing through the suction port exclusively flows in the direction perpendicular to the contour line that forms the hole of the suction port. Therefore, it can be said in connection with the contour line of the suction port that the greater the length of the contour on the distal end side of the suction valve, the easier it becomes for the gas to flow towards the distal end side of the suction valve. The suction port described in Japanese Unexamined Patent Publication (Kokai) No. 2000-54961 is superior to the circular suction port described in Japanese Unexamined Patent Publication (Kokai) No. 57-97974 because the gas passing through the suction port can flow more easily from the distal end side of the suction valve in its longitudinal direction in the former than in the latter. Therefore, the ease of the inflow of the gas is higher in the suction port of Japanese Unexamined Patent Publication (Kokai) No. 2000-54961 than in the circular suction port of the Japanese Unexamined Patent Publication (Kokai) No. 57-97974.
The position of the suction port in the circle of the circumferential surface of the cylinder bore as viewed in the reciprocating direction of the piston is close to a circumferential line of the circle of the cylinder bore, based on the relationship with the discharge port. In the contour line of the suction port described in Japanese Unexamined Patent Publication (Kokai) No. 2000-54961, a portion of the contour line close to the circumferential line of the circle of the cylinder bore is spaced apart, progressively, from the circumferential line of the circle of the cylinder bore as it extends away to the right and left from the center line of the suction port (represented by X in the drawing). The degree of separation is smaller, in comparison, than in the case of the circular suction port. The gas can more easily flow from the distal end side of the suction valve in its longitudinal direction in the suction port described in Japanese Unexamined Patent Publication (Kokai) No. 2000-54961 than in the circular suction port. Therefore, as to ease of the inflow of the gas, the suction port of Japanese Unexamined Patent Publication (Kokai) No. 2000-54961 is superior to the circular suction port of Japanese Unexamined Patent Publication (Kokai) No. 57-97974.
The construction in which the portion of the contour line close to the circumferential line of the circle of the cylinder bore is spaced apart progressively to the right and left from the center line of the suction valve makes it easy for the gas flowing in a direction crossing the portion of the contour line close to the circumferential line of the circle of the cylinder bore to flow in the direction of the circumferential line of the circle of the cylinder bore. However, such a flow of the gas is not desirable from the aspect of the ease of the inflow of the gas into the cylinder bore.
The object of the present invention is to provide a piston type compressor which can improve the ease of the inflow of the gas when the gas is sucked from the suction port to the cylinder bore.
To accomplish this object, the present invention provides a piston type compressor comprising a housing having cylinder bores, a suction chamber, a discharge chamber, suction ports and discharge ports formed therein, pistons reciprocatingly arranged in the cylinder bores, a drive shaft rotatably supported by the housing, a transmission mechanism operatively coupled to the drive shaft and the pistons for converting rotation of the drive shaft into reciprocal movement of the pistons, suction valves to open and close the suction ports, and discharge valves to open and close the discharge ports. The suction valve has a proximal end portion and a distal end portion on the opposite side of the proximal end portion, the distal end portion of the suction valve having an outer contour line including a distal end forming line located near a circumferential surface of the cylinder bore and side lines located on either side of the distal end forming line, the suction port having a contour line including a distal end line located near the circumferential surface of the cylinder bore and side lines located on either side of the distal end line. The distal end forming line of the suction valve and the distal end line of the suction port are arranged along the circumferential surface of the cylinder bore, so that a gap between the distal end forming line and the distal end line with respect to a radial line of a circle forming the circumferential surface of the cylinder bore is substantially constant and a gap between the distal end forming line and the circumferential surface of the cylinder bore with respect to the radial line is substantially constant.
The construction in which the gap between the distal end forming line of the suction valve and the distal end line of the suction port and the gap between the distal end forming line and the circumferential surface of the cylinder bore are substantially constant makes it easier for the gas to flow between the circumferential surface of the cylinder bore and the distal end forming line of the suction valve in a returning direction of the piston. Such a gas flow is desirable for improving ease of the inflow of the gas into the cylinder bore.
Preferably, an average of the gap between the circumferential surface of the cylinder bore and the outer end forming line of the suction valve is greater than a gap between the suction valve and the distal end line of the suction port under a maximum valve open condition.
The gas that flows between the suction valve and the distal end line of the suction port so as to perpendicularly impinge against the circumferential surface of the cylinder bore can more easily flow between the circumferential surface of the cylinder bore and the distal end forming line of the suction valve in the returning direction of the piston.
Preferably, a middle line is provided which passes through a middle point of a maximum length of the suction port in a longitudinal direction of the suction valve, extends transversely with respect to the suction port and crosses a reference line extending in the longitudinal direction of said suction valve, the middle line dividing the suction port into a first section positioned on the side of the proximal end portion of the suction valve and a second section positioned on the side of the distal end of the suction valve, an area of the second section being greater than an area of the first section.
The construction in which the area of the second section is greater than the area of the first section makes it easier for the gas passing through the suction port to flow from the distal end side of the suction valve.
Preferably, a width increasing region is disposed in which the width of the suction port in a direction of the middle line becomes gradually greater from the proximal end side to the distal end side of the suction valve in the longitudinal direction of the suction valve, and the length of the width increasing region in the direction of the reference line occupies a major part of the maximum length of the suction port in the direction of the reference line.
The existence of the width increasing region makes it easier for the gas passing through the suction port to flow towards the distal end side of the suction valve.
Preferably, a maximum width of the suction port in the direction of the middle line exists in the second section and is greater than the maximum length of the suction port in the direction of the reference line.
The construction in which the maximum length of the suction port in the direction of the reference line is smaller than the maximum width of the suction port in the direction of the middle line and the maximum width of the suction port in the direction of the middle line exists on the side of the second section is convenient for increasing the length of the contour line of the suction port on the distal end side of the suction valve.
Preferably, the contour line of the suction port includes a proximal end line positioned on the side of the proximal end of the suction valve, said distal end line and a pair of right and left side lines, and the distal end line is longer than the proximal end line.
The construction wherein the length of the distal end line is greater than that of the proximal end line makes it easier for the gas passing through the section port to flow towards the distal end side of the suction valve.
Preferably, the contour line of the suction port includes a pair of first connection lines connecting the proximal end line to the pair of side lines and a pair of second connection lines connecting the distal end line to the pair of side lines, the pair of first connection lines being smoothly connected to the proximal end line and the pair of said side lines, the pair of second connection lines being smoothly connected to the distal end line and the pair of side lines.
Preferably, the contour line of the suction port is an annular line with no corner. The construction wherein the contour line of the suction port is an annular line with no corner is advantageous for preventing backflow of the gas from the cylinder bore to the suction port.
Preferably, the contour line of the suction port is an annular convex line with no corner.
Preferably, the reference line extends substantially along the radial line of the circle of the circumferential surface of the cylinder bore.
The construction wherein the reference line extends substantially along the radial line of the circle of the circumferential surface of the cylinder bore is advantageous for bringing the contour line of the suction port on the distal end side of the suction valve closer to the circle of the circumferential surface of the cylinder bore.